This invention pertains generally to styrenic polymer blends or polyblends and particularly to rubber modified styrenic polymer blends or polyblends with improved properties.
Rubber modified styrenic polymer compositions are well-known in the prior art. These rubber modified compositions are commonly known and referred to as graft copolymers or polyblends. The rubber modified styrenic polymer compositions have improved properties as compared to the non-modified styrenic polymers. Styrene (S) acrylonitrile (AN) copolymers (SAN), for instance, have improved toughness and high impact resistance when they are rubber modified to get materials called acrylonitrile-butadiene-styrene copolymers (ABS). This improvement in the properties results from rubber particles being dispersed in the SAN continuous or matrix phase. ABS polymers have become particularly important in the automobile and appliance industries.
It is known that improved physical properties such as excellent thermal stability and improved heat resistance are obtained when fumaronitrile is copolymerized with a vinyl aromatic hydrocarbon like styrene. U.S. Pat. No. 2,417,607 describes such copolymerization products. U.S. Pat. No. 2,439,226 describes that a copolymer, for example, of alpha-paradimethyl substituted styrene with a mixture of acrylonitrile and fumaronitrile has better heat-resistance than a copolymer of alpha-paradimethylstyrene and acrylonitrile.
Styrene acrylonitrile copolymers (SAN) have been rubber modified with grafted rubber concentrates with fumaronitrile styrene (FNS) copolymer in the grafted phase to give styrenic polymer blends that are colorless and have enhanced solvent resistance. Such styrenic polymer blends have been described in German Patent 1 264 767. This improvement in the property results from FNS grafted rubber particles being dispersed in a SAN matrix phase. These polymer blends have relatively minute weight percent of fumaronitrile which although sufficient to impart improved solvent resistance is not sufficient to impart significantly improved heat resistance to these polymer blends.
It is an object of the present invention to obtain rubber modified styrenic copolymer resins containing fumaronitrile (FN), having binary SAN copolymer grafted rubber concentrate dispersed in a SFN or a SANFN copolymer matrix phase with improved properties for applications such as automobile body panels. Both heat and solvent resistance are needed, as the body panel substrate is subjected to paint solvents and paint oven temperatures of 230.degree.-270.degree. F. during fabrication, and occasional exposure to stress crack agents as a finished part.
Since both rubber dispersion and the adhesion of the grafted rubber phase to the continuous matrix phase in impact modified blends determine the morphology, failure mechanisms, and ultimately, the physical properties of the blends, it is yet another object of the present invention to provide rubber-modified blends having improved compatibility or miscibility as between the SFN or SANFN copolymer matrix and the SAN copolymer in the graft phase of the impact modifier. Phase separation is undesirable as it causes poor toughness in rubber reinforced polymeric blends. Accordingly, it is highly desirable to provide polyblends which have improved compatibility between the continuous matrix and the dispersed grafted rubber phases and which thereby exhibit enhanced toughness and impact resistance.
Improved compatibility as between an SAN binary copolymer phase and an SFN or SANFN phase is also important to physical property and performance characteristics in the context of non-rubber modified polymer blend compositions containing the indicated types of individual copolymer ingredients. Accordingly, it is another object of the present invention to provide non-rubber modified polymer blends of the type mentioned which have improved compatibility as between the individual polymer ingredients and which thereby exhibit improved physical properties.